<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<style>
    .a {
        height: 100px;
        margin-bottom: 100px;
        background-color: blue;
    }

    .b {
        height: 100px;
        margin-top: 100px;
        background-color: black;
    }
</style>

<body>
    <div style="overflow: hidden;">
        <div class="a"></div>
    </div>
    <div class="b"></div>
</body>

</html>